I. Field of the Invention
The present invention relates to communication. More particularly, the present invention relates to a novel and improved method and apparatus for providing communication over a digital link.
II. Description of the Related Art
A variety of apparatus exists today that use standard telephone networks to convey data from one terminal to another. One of the most common terminals that uses a standard telephone network to convey data is the facsimile (FAX) machine. Like other terminal equipment that use standard telephone networks, a FAX machine uses a modem to translate digital information to audible analog tones for transmission over the telephone network. At the receiving FAX machine, a modem is used to convert the tones back into an estimate of the original digital information sent by the transmitting FAX machine.
With the deployment of cellular and personal communications wireless systems, the end user may wish to connect his terminal equipment to a mobile communications device instead of directly to a land telephone network. If the end user attempts to send the audible tones produced by a modem over a standard digital wireless channel, it is doubtful that he will be successful. Digital wireless communication equipment typically uses vocoders to convert incoming voice signals into digital bits for transmission over the channel. Vocoders are tailored to sample and compress human voice. Because modem tones differ significantly from human voice, the vocoder can cause critical degradation to the modem tones. Also, maximizing the capacity of the system in terms of the number of simultaneous users that can be handled is extremely important in a system using a wireless link. Digitizing modem tones with a vocoder and sending them over the digital wireless link is an inefficient use of the radio channel.
A more efficient, flexible, and reliable transmission means is to provide a mechanism to transmit the digital data over the digital wireless link directly. This configuration presents some unique opportunities to take advantage of the digital link to provide high quality service.
Just as the vocoder is not suited for the transmission of analog data tones, the digital data transmission circuitry is not suited for the transmission of voice. In standard modem setups that use analog data tones, the end user is able to listen to the tones received from the answering modem. This ability is especially important when the connection fails. Without the ability to listen to the returning signal, the end user may be unable to detect the cause of a failure to connect. Connection failures can occur in many ways including dialing the wrong number, temporary interruptions of service, connection to an out-of-service line, connection to a human answerer, or receipt of a busy signal. These types of occurrences are difficult for the modem itself to detect. Without the audible feedback feature, the end user may only know that the connection failed thus be unable to correct for the failure. The present invention abrogates this problem by providing an audible feedback feature to the mobile unit user which provides similar audible feedback available today with conventional modems.
It is therefore the object of the present invention to provide an efficient method and apparatus for providing a audible feedback feature during a data call.
It is a further object of the present invention to provide a means for monitoring the progress of the modem connection process.